1. Field of the Invention
The invention relates to an eccentric pump with lock valve which can operate with both directions of its rotational drive, as with lubricant circulation of drives often the case is. The eccentric pump comprises:
a stationary outer casing having two parallel side walls and a cylindrical inner surface between the side walls, and further having inlet and outlet openings being sealingly separated and terminating in the cylindrical inner surface, PA1 a shaft arranged within the casing concentrically to the cylindrical inner surface and having a cylindrical surface being eccentric to the shaft as well as to the cylindrical inner surface of the casing, PA1 a circular sealing ring being sealingly displaceable in respect of the eccentric surface of the shaft as well as to inner wall portions of the casing, and further having a radial slot sealingly engaging a stationary pin with its both limiting surfaces. PA1 a stationary outer casing having two parallel side walls and a cylindrical inner surface between the side walls, and further having inlet and outlet openings being sealingly separated and terminating in the cylindrical inner surface, PA1 a shaft arranged within the casing concentrically to the cylindrical inner surface and having a cylindrical surface being eccentric to the shaft as well as to the cylindrical inner surface of the casing, PA1 a circular sealing ring being sealingly displaceable in respect of the eccentric surface of the shaft as well as to inner wall portions of the casing, and further having a radial slot sealingly engaging a stationary pin with its both limiting surfaces. PA1 an inner slide member is arranged between the casing and the circular sealing ring, the slide member being sealingly but moveably attached to inner surfaces of the casing, and the slide member being rotatable between a first position and a second position, and PA1 the casing has two inlet openings and at least one outlet opening, and PA1 the slide member has two through bores, the first through bore is in communication with one inlet opening, the second through bore with at least one outlet opening, in the first position of the slide member, and the first through bore is in communication with at least one outlet opening, the second through bore with the other inlet opening, in the second position of the slide member, and PA1 the pin is fixed to the slide member and is sealingly separating the through bores from each other.
2. Description of the Related Art
In the prior art, eccentric pumps with lock valve (as described in detail in e.g. U.S. Pat. No. 4,737,089) have been proposed to eliminate the drawbacks of the conventional pumps such as gear pump, screw pump, rotary pump, etc. These units are quite complex assemblies containing twenty to thirty pans, they are quite voluminous, they cannot be mounted on the shaft of a drive directly but they need a free shaft end and/or separate power transmission unit such as gears or chain. Further, they are sensible to failures and frequent control and replacement are necessary with them. The eccentric pump proposed earlier is, in contrast, a simple construction with easily producible minimal number of pans, and it can directly be mounted on the shaft of the drive with a reduced space requirement.
In the eccentric pump, the space between the pump casing and the eccentric rotary pan is divided during rotation by the contact point of the casing and the rotary part and by the lock valve into an expanding suction chamber and a reducing pressure chamber while the contact point moves from the suction inlet of the pump towards its pressure outlet. With this, liquid is sucked into the suction chamber and discharged from the pressure chamber.
The practice has shown, however, that the conventional eccentric pumps are not suitable in applications, wherein the direction of rotation to be used for driving the pump can be reversed during operation. As it will be clear from what have been said above, the eccentric pump will not forward liquid any more if the driving shaft rotates in the reverse direction. The more, it will suck away the liquid which have been transported by the eccentric pump earlier, during the operational rotation. This feature simply excludes eccentric pumps from using them with drives wherein the operation of the drive in reverse rotational direction often occurs. In reverse rotation, the load on the drives is often greater than normally, therefore, the drive cannot remain without any lubricant and cooling medium. In the prior art, it is not known to use eccentric pumps in applications wherein bidirectional rotational operation can occur.